Recovery of oils by steam injection



Nav. 4, 1969 S. HAYNES, JR.. ETAL RECOVERY OF OILS BY STEAM INJECTION Filed Dec. 14, 1967 U.S. Cl. 6 Claims ABSTRACT OF THE DISCLOSURE A method of recovering hydrocarbon materials from a subterranean hydrocarbon-bearing formation by means of injecting wet steam therein, wherein the liquid phase of the wet steam has been treated separately with an anti-clay swelling agent in order to permit a more even penetration of the formation by the flooding fluid.

BACKGROUND OF THE INVENTION This invention pertains generally to an improved method of recovering hydrocarbons from a subterranean hydrocarbon-bearing formation, and more particularly to one wherein wet steam treated with an anti-clay swelling agent is injected into the formation in order to improve the flow. characteristics thereof.

Recovery of hydrocarbons from subterranean formations by means of liquid and gaseous floods injected into the formation are today-common practices in the petroleum industry. The introduction of these flooding fluids in the form of heated .tluids has been found desirable, particularly in those formations containing highly viscous hydrocarbon' materials. Steam flooding is notably well suited for this purpose, since the energy contained therein effectively reduces the viscosity of the hydrocarbons and allows production thereof. Inforder to realize the maximum viscosity reduction of the hydrocarbons, the injected steam should impart the maximum heat to the formation, as is consistent with economical steam generator design, and provide a uniform penetration of the formation Under certain circumstances, present day steam floods fail to permit recovery of large quantities of hydrocarbons contained in the formation. Such is particularly true when the ilooding fluid tends to finger or channel through the hydrocarbonbearing formation, rather than providing a solid front moving outwardly from the well in the form of an expanding circle. The fingering of the flooding fluid bypasses an appreciable portion of the hydrocarbon-bearing formation and leaves hydrocarbons untouched. Steam ooding is-particularly susceptible to such lingering, an effect which is most pronounced when the viscosity of the hydrocarbons encountered increases. Thus, it is desirable to provide a method of steam flood ing which imparts the maximum heat to the underground hydrocarbon-bearing formation, without any detrimental effect on the steam generator while premeating the formation in an expanding manner.

SUMMARY OF THE INVENTION The invention provides an improved method of generating wet steam from a previously softened water supply, subsequently separating the liquid phase from the vapor phase of the generated wet stream wherein the liquid phase thereof is treated with an anti-clay swelling agent and injected in combination with the vapor phase of the wet steam into a well in communication with a hydrocarbon-bearing formation, thereby providing a steam flood imparting maximum heat to the formation and permeatlng the same in a uniformly expanding manner.

United States Patent O 3,476,183 Patented Nov. 4, '1969 As previously discussed, one of the primary shortcom-1 ings of the present are utilizing steam floods in hydro`1 carbon-bearing formations is the lack of uniform penetration thereof. The present invention utilizes in combination with the heat provided by a steam ood, the injection of anti-clay swelling agents in order to provide a more uniform penetration of the formation by the steam flood. It is noted however, that the introduction of these anti-clay swelling agents into the steam generator feed water produces limitations on the quality of the steam that may be produced. Production of steam with a high volume percentage of vapor, i.e., steam with a high quality, will cause the concentration of the additive introduced in the feed water to exceed the saturan tion point during the steam generation process. Should this occur, the salts therefrom will be deposited on surfaces, e.g. tubes, within the steam generator and thus shorten the time the steam generator can be used before its eciency is decreased to a point where tube cleann ing is necessitated.

To avoid deposits in the steam generator created by additives desirable to better permeate the formation, the method of the present invention provides a means for the introduction thereof subsequent to the generation of the steam. Wet steam is generated from a supply of water treated to 'reduce the hardness thereof, wherein the liquid content lof the generated wet steam is separated therefrom and separately treated with the desired addiu tives, and subsequently injected into the hydrocarbonu bearing formation in combination with the vapor phase of the steam.

Accordingly, it is an overall object of this invention to provide a method of injecting steam in combination with anti-clay swelling agents into a hydrocarbon-bearing -formation to improve the ow characteristics thereof.

Another object of this invention is to provide a method of recovering hydrocarbon materials by means of injecting steam into a hydrocarbon-bearing formation whereby additives may be introduced into the steam flooding fluid without any detrimental effects on the steam generating apparatus. f,-

These and other..objects, advantages and features 0f the invention will become more apparent from the foln lowing description taken in conjunction with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING The drawing depicts a schematic elevation view of an injection and recovery well in conjunction with the steam treating apparatus.

DESCRIPTION OF THE PREFERRED EMBODIMENT The objects of the invention are accomplished by employing a method wherein wet steam having a liquid phase and a vapor phase is generated from a softened feed water supply, separating the liquid. phase from the vapor phase, contacting the liquid phase with an anti= clay swelling agent, and injecting in combination the treated liquid phase with the vapor phase into the hy drocarbon-bearing formation.

With reference to the drawing, -the method of the invention is accomplished by an apparatus comprising a feed water tank indicated at 10, which provides a source or water for the steam generator 11. The feed water is supplied to the steam generator through water line 12, the flow therethrough being controlled by valve 13. In the event that the feed water supply is hard, in that it contains alkali earth metal ions, as is typical in the water locally available in oil fields, tank 14 is utilized to supply additives which will soften the feed water supply. The additives are introduced to the feed water tank 10 through `Methods of treating water are quite common in the art and include such treating methods as lime-soda, -hot phosphate softening, or passing the water through a packed bed of sodium zeolite. In addition, chlorination, aeration or deaeration and coagulation may prove beneficial in such treatment. Generally such treatments are desirable to reduce corrosion inthe steam generating apparatus and reduce the servicing required by such apparatus. Any of the aforementioned methods will suf'lice, and in practice, it has been found desirable to generate the wet steam from a feed water supply containing not more than 2500 p.p.m. of total solids, p.p.m. hardness, l p.p.m. dissolved oxygen and with a pH value between 9 and 10.

However, even with a softened feed Water, the production of too high a volume percentage of steam vapor will cause the concentration of salts contained in the softened Water to exceed the saturation point during the steam generating process. This would cause salts to be deposited on the steam generato-r tubes and thus shorten the time that the steam generator can be used before its efficiency is decreased to a point where tube cleaning becomes necessary. Therefore, in order to lengthen the service life of the steam generator, itis desirable to generate a s-team containing sufficient liquidwater phase to act as a vehicle for carrying the dissolved salts from the steam generator and maintain the concentration of salts below the saturation point. Furthermore, when steam is injected into a hydrocarbon-bearing formation, maximum exploitation is effected when the maximum heat is imparted to the formation. This is best accomplished by utilizing a steam containing as low a liquid water phase as is consistent with the steam generator service life. Based on these considerations, a steam wherein the liquid water phase does not exceed 5 volume percent as a lower limit, and with an upper limit of 0.05 volume percent will provide optimum results.

To measure and control the quality of the wet steam, i.e., the percent liquid phase, produced by the steam generating apparatus, a method and apparatus as disclosed in the copending, coassigned application for patent for Method and Apparatus for Measuring Steam Properties, Ser. No. 686,931, filed Nov. 30, 1967, the disclosure of which is incorporated herein by this reference thereto, may be utilized. Therein is disclosed, a method and apparatus by which the quality of steam flowing from a steam generator is determined by expanding adiabatically a sample of the wet steam and separating a portion of the liquid contained in the expanded wet steam at saturation conditions. The enthalpy of the sample is the same as that of the steam supplied by the generator due to the adiabatic expansion process. The quality of the expanded sample of wet steam may be measured, as disclosed therein, by means of comparing the conductivity or chloride ion concentration of the feed water to that of the liquid separated from the sample. The quality of the steam supplied by the steam generator then may be determined by measuring the temperature or pressure thereof. The method of the incorporated disclosure provides a simple and expedient means for determining or controlling the quality of the wet steam such that it does not exceed preferably the desired 5 volume percent of liquid phase water.

With reference to the drawing, the generated wet steam ows through steam line 17 to a liquid-vapor separator indicated generally at 18. Valve 19 provides a means for regulating the wet steam flow through line 17. The liquidvapor separator `18 provides a means for separating the liquid phase from they vapor phase, whereby" the vapor phase exits through steam line'20 and valve 21, arid is subsequently injectdlnto well Thellyyliquid'lsepa'rated from the wet steam exits from the liquid-vapor separator 18 and flows through ow line 22 into the treatment apparatus 23. Treatment apparatus 23 is utilized to impart an anti-clay swelling agent to the liquid phase separated from the generated wet steam. Steam flooding, like water flooding, is concerned with the effect that the injected fluids exhibit on the underground hydrocarbon-bearing formation. Often these hydrocarbon-bearing formationsl contain certain amounts of swelling clays inthe form of a bentonite or a montmorillinite clay, which upon swelling, reduce the permeability of the formation. Treating the liquid phase with sodium chloride, guanidine hydrochloride, or other surface active agents, by means of the treatment apparatus 23, are some of the methods, although others are not precluded, which will prevent the swelling of clays in the formation and thereby reduce the tendency of the ooding fluid to finger through the hydrocarbon-bearing formation. It should be noted also that it may be desirable to treat only a portion of the liquid phase with the anti-clay swelling agent. This may be accomplished by separating the liquid phase from the generated wet stream, treating the desired portion of the liquid phase, and then combining the treated portion with the vapor phase, while the remainder of the liquid phase, i.e., the untreated portion, may Ibe recycled as feed water.

After the liquid has been treated suitably, it exits from the treatment apparatus 23 and flows through flow line 24 containing therein a control valve 25 and is recombined with the vapor phase flowing through steam line 20. The amount of liquid to be recombined with the vapor phase may be regulated by means of the venturi indicated at 26. The recombined liquid and vapor phases are injected into well 40 by means of the well tubing 41 whereby the steam is then discharged into the hydrocarbon-bearing formation 60. Packer 42 is placed in the well 40 in order to close the annular space 43 between the casing 44 and the tubing 41, and the bottom of the well 40 may be closed by conventional means, e.g. cementing, 30, in-order to direct the steam flood into the formation 60. It should be noted that alternative means may be provided whereby the liquid phase may be injected into the formation through the annular spacing 43 in lieu of being recombinedwith the vapor phase prior' to injection. After sufficient time has elasped to allow the injection of wet steam to sufficiently heat the formation, valves 21 and 25 may be shut and the well permitted to produce by opening valve 45 and producing through lineA 46.

.The methodcf this invention may also utilize the steam injection as a driving uid wherein well 40 is'then used as an injection well and ano-ther well S0, spaced therefrom, is used as a recovery well, with hydrocarbons being produced through line 51 and controlled by valve 52.

v Thus, there has been shown and described an improved method of injecting wet steam in combination with an anti-clay swelling agent into a hydrocarbon-bearing formation to improve the flow characteristics thereof without any detrimental effect on the steam generating apparatus.

Other modifications and variations of the invention as hereinbefore set forth may 'be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claims.

We claim:

1. A method of recovering hydrocarbons from a subterranean hydrocarbon-bearing formation traversed by a well which comprises generating wet steam from a supply of softened feedwater, said wet steam containing a vapor phase and a liquid phase, said liquid phase comprising less than 5% by volume of said feed water, separating -said liquid phase from said vapor phase, treating said liquid phase with an anti-clay swelling agent, injecting said vapor phase andithe treated yliquid phase into said Well 'and'.contacting said'subterranean formation there- 2. The method of claim 1, wherein the generated wet steam contains more than 0.05% by volume of water in said liquid phase.'

3. The method of claim 1, wherein said treating of said liquid phase with said anti-clay swelling agent comprises contacting said liquid phase with sodium chloride.

4. The method of claim 1, wherein said treating of said liquid phasewith said anti-clay swelling agent com= prises contacting said liquid phase with guanidine hydrochloride.

5. The method of claim 1, wherein said treating of said liquid phase with said anti-clay swelling agent involves only a portion of said liquid phase, and combining said portion with said vapor phase and injecting such combination into said well, the remainder of said liquid phase being recycled as part of said feed water.

6. A method of recovering hydrocarbons from a subterranean hydrocarbon-bearing formation traversed by an injection well and a producing well spaced therefrom which comprises generating wet steam from a supply of softened feed water, said wet steam having therein a liquid phase and a vapor phase and being in the quality range of more than 95% and less than 99.95% by volume, separating said liquid phase from said vapor phase, treating said liquid phase with a clay anti-swelling agent, and injecting said vapor phase and the treated liquid phase into said injection well thereby heating said subterranean formation and causing hydrocarbons contained therein to flow into said producing well for recovery therethrougha References Cited UNITED STATES PATENTS 3,l41,501 7/1964 Bernard et al. 166-9 3,237,692 3/1966 Wallace et al. 166-40 3,353,593 11/1967 Boberg 166-40 X 3,360,043 12/1967 Braden et aL 166-11 X 3,379,249 4/ 1968 Gilchrist et a1, 166-11 STEPHEN J. NOVOSAD, Primary Examiner U.S.. Cl. X.R. 

